Unless your daughter is going to be a future basketball player, I think you need to wait about four or five years yet for a 10/22. I have quite a few issues with allowing a child a semi-automatic for their first weapon. The first of that is you are trying to teach control, as well as gun safety, and it's just too easy to pull the trigger as quick as she can.
For a six year old, I like the Crickett rifles, the Savage Cub or the CZ Scout. So many people will give you grief over buying your daughter a Crickett, but everything I've seen about them makes them a great starter rifle. One nice thing about the Crickett is the low price, you don't have to spend a fortune on one. You can get a
Walnut stocked one relatively inexpensively, with a peep sight. Or, you can get a pink laminate one. Don't get the synthetic stocked ones.
For a few dollars more, Savage gives you a much better choice, and a better made rifle. You can get them with the AccuTrigger. Here's the
Pink laminate single shot. Again, with peep sights in the rear.
This is the Savage Mk I Youth rifle. It has open sights, and is drilled and tapped for mounting a scope later on. It's a little bit longer than the others ones I've shown you so far, but also gives your daughter room to grow into instead of growing out of.
Finally, I can think of no finer rifle to start your daughter off into the shooting world than the
CZ 452 Scout. This is the only rifle out of all that I've listed that is not a single shot rifle, it has a magazine that can hold five rounds. Actually, I believe it comes with a single shot adapter, and will fit the standard five and ten round mags.
You will notice that all of the rifles I have recommended are no longer than 33", most with a 16.5" barrel, and under 5 pounds. All are bolt action, and single shot. This means that your daughter has to work at getting the rifle to fire, and it's easier to control safety, and she also learns an appreciation of the rifle and what it takes to set up each shot, instead of just blastinatin'! :Blasting_
Don't handicap your daughter by giving her a rifle that isn't going to fit her and making it harder to shoot. She'll appreciate the 10/22 one day, no doubt, but like I said, wait four or five years until she's ready for it. In the meantime, give her something that she can enjoy and have a reasonable chance of shooting well.
As to your original question, iron sights at 15-25 yards.
G